The effect of substituents on geminal proton–proton coupling constants. III
| Autor: | Roger N. Renaud, John W. Bovenkamp, Robert R. Fraser, Raj Capoor |
|---|---|
| Rok vydání: | 1977 |
| Předmět: | |
| Zdroj: | Canadian Journal of Chemistry. 55:2642-2648 |
| ISSN: | 1480-3291 0008-4042 |
| DOI: | 10.1139/v77-368 |
| Popis: | The effect of substituents at the 3-position in a series of N-methyl 5,6-dihydro-7H,12H-di-benzo[c,f]azocines on the geminal coupling constants of the C-12 methylene protons has been determined. The slope of the Hammett plot of 2J vs. σ has been found to be +0.20. The orientation of the methylene protons with respect to the π orbitals of the benzene ring bearing the substituent is such that no hyperconjugative effect should be present. The value of +0.20 is in contrast to a previously measured slope of −1.9 for compounds having a geometry ideal for hyperconjugative effects and substantiates the predictions of theoretical MO calculations. As a result, the reliability of this conformational dependence of ρ for use in conformational analysis has been strengthened.A comparison of the data for the azocines with those in the literature indicates the difference between the minimum and maximum effects of a phenyl substituent on a geminal coupling constant of an attached methylene group is 5.5 Hz. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|